1. Field of the Invention
The present invention relates to a control system for the rectilinear vertical reciprocating movement of a needle-holder beam in a needling machine.
2. Description of the Related Art
It is known that, during operation of needling machines for manufacturing non-woven fabrics, the needle-holder beam must be driven in a vertical reciprocating manner, with the movement of the beam being transmitted by a crank mechanism, usually formed by two counter-rotating connecting rods. Because of evident technical reasons, the movement of the beam must occur in a vertical direction, as the needles it supports must enter the material to be processed with as minimum an inclination as possible.
Various systems are used to control the vertical movement of the needle-holder beam. For example, guides installed on a side of the needle-holder beam support, or systems having adjustable slide gibs have been used. However, in both cases, due to the wide sliding surface, a danger of seizing exists, and, further, when slide gibs are used, it is very difficult to adjust the related clearances. Further, it is possible to have a loss of lubricant, resulting in damage to the product submitted to process.
Guide sliding blocks in an oil bath or mechanisms derived from Watt's parallelogram have also been proposed. However, as in the case of sliding blocks, the danger of loss of oil, resulting in damage to the product, still exists, and, in the case of Watt's parallelogram, the capability of reaching very high running speeds is minimal, and, in any case, the mechanism is complex and cumbersome from the viewpoint of construction and development.